Reflective spatial light modulator with high spatial frequency border

ABSTRACT

A spatial light modulator having an active and a peripheral region, wherein coherent light impinges on both regions, but due to a higher spatial frequency of pixels within the peripheral region, and due to biasing the peripheral region pixels to maximize dispersion of reflected light therefrom, a majority of light reflected from the peripheral region is directed outside of a three-dimensional target window. A spatial frequency of the pixels in the active region is selected such that maximum dispersion of reflected light from the active region is incident within the three-dimensional target window. In this way, incident light that does not reflect from the active region need not be absorbed, or blocked, but instead can be reflected, but still fails to interfere with the target window.

CLAIM OF PRIORITY UNDER 35 U.S.C. § 119

The present application for patent is a continuation of U.S. patentapplication Ser. No. 15/666,384 entitled “REFLECTIVE SPATIAL LIGHTMODULATOR WITH HIGH SPATIAL FREQUENCY BORDER” filed Aug. 1, 2017, whichclaims priority to Provisional Application No. 62/369,490 entitled “HIGHSPATIAL FREQUENCY BORDER” filed Aug. 1, 2016, the disclosures of whichare incorporated herein by reference in their entireties.

FIELD OF THE DISCLOSURE

The present application relates to optical phase modulation, and morespecifically to beam steering using optical phase modulation.

DESCRIPTION OF RELATED ART

Spatial Light Modulators (SLM) are devices for imprinting information onoptical beams. This information may be in the form of amplitudemodulation, phase modulation, or both. These devices may be controlledoptically or electronically. See, for example, “Spatial Light ModulatorTechnology: Materials, Devices, and Applications (Optical Science andEngineering)”, Efron, (Pub. CRC press, 1994), or “Introduction toMicrodisplays”, Armitage, et al. (Pub. Wiley, 2006), for anotheroverview of the field. In some applications the output of an SLM can usethe optical Fourier Transform or diffraction pattern from the SLM. See,for example, “Introduction to Fourier Optics”, (J. Goodman, Pub. Roberts&Co., 2005), for a general introduction to the field of Fourier Optics.

Many SLMs have an active area of controllable elements, referred to as“pixels” even though they are often not simple visual “pictureelements”. As shown in FIGS. 1 and 2, wherein the incident beam extendsbeyond the pixels, portions of the beam will reflect off the substratewithout control and this light can contribute to a bright “zero-order”,or “zero-spatial-frequency” (ZSF) spot that can be undesirable in someapplications.

FIG. 1 illustrates an SLM system 100 where light from a source 110 isreflected off an SLM 104 having a pixel array 102. A first portion 106of the SLM 104 reflects the beam, and the beam extends beyond the pixelarray 102. A second portion 108 of the SLM 104 does not see incidentlight (where an edge of the beam is defined by D4σ, 10/90, 20/80,knife-edge, 1/e², full-width half max, or D86 for intensity falloff fromthe beam center or beam maximum). The SLM 104 uses a Fourier system toreflect the beam through a lens 112 (e.g., a Fourier lens), or multiplelenses, into a target range of angles (or a target volume in someapplications). As shown, the SLM 104 is used to focus multiple spots oflight within a target volume, where each spot of light has x, y, and zcoordinates. A zero-order spot 118 results from a portion of the beamreflecting off a portion of the SLM that is outside or surrounding thepixel array 102.

The pixels can be individually-addressed to modulate the phase and/oramplitude of the incident light. Outside the pixel array 102 there maybe a border region that can be electrically driven to a phase and/oramplitude value if desired. In some cases a mechanical feature (e.g.,adhesive gasket or a frame, to name two) may be implemented in theregion outside the pixel array 102 to block or absorb the incidentlight. However, it can be impractical to precisely position such astructure adjacent the pixel array 102, and thus unwanted reflectionsfrom this region may still occur, thereby leading to a failure toalleviate the zero-order spot 118.

Prior art spatial light modulators have been constructed with “dummy”pixels around the periphery of the active pixel array. The dummy pixelsare not individually addressable, and are designed to improve uniformityduring the device construction process. These are typically electricallyconnected together and may be driven to some phase and/or amplitudevalue if desired.

Some have sought to alleviate the zero-order spot by underfilling theactive area. FIGS. 3 and 4 show an SLM arranged to underfill the activearea. This technique involves arranging the optical system to reduce thesize of the incident beam. There may be a region 302 that receivesfull-intensity illumination and another region 303 that receivesreduced, or greatly reduced, intensity of illumination. This techniquedoes alleviate the zero-order spot, but reduces device performance sinceactive pixels are “wasted” by not being properly illuminated and so areunable to contribute their information to the beam.

Other methods use the setup of FIGS. 1 and 2, but try to block incidentlight from the peripheral area where there are no active pixels.However, such systems are impractical in practice. For instance, U.S.Pat. No. 6,700,557, which discloses amplitude modulating SLMs, usesperipheral pixels that are biased to “black” or to be largely absorbingrather than reflective. However, for phase-modulating SLMs there is nophase equivalent to “black.” Thus, other approaches are desired.

SUMMARY OF THE DISCLOSURE

The following presents a simplified summary relating to one or moreaspects and/or embodiments disclosed herein. As such, the followingsummary should not be considered an extensive overview relating to allcontemplated aspects and/or embodiments, nor should the followingsummary be regarded to identify key or critical elements relating to allcontemplated aspects and/or embodiments or to delineate the scopeassociated with any particular aspect and/or embodiment. Accordingly,the following summary has the sole purpose to present certain conceptsrelating to one or more aspects and/or embodiments relating to themechanisms disclosed herein in a simplified form to precede the detaileddescription presented below.

Some embodiments of the disclosure may be characterized as a spatiallight modulator having a plurality of individually-addressedphase-modulating pixels. The pixels can be configured to reflect andmodify phasing of a beam of coherent light incident on the spatial lightmodulator to produce reflected light. The phasing can be controlled tosteer the reflected light into a target range of angles. The SLM caninclude a substrate, a first array of individually-addressed reflectivephase modulation pixels on the substrate, a first biasing circuitrycoupled to the first array, a second array of border pixels on thesubstrate, and a second biasing circuitry coupled to the second array.The first array can have a first spatial frequency of N and can beconfigured to apply a plurality of phase modulations to a centralportion of the beam. The first biasing circuitry can bias the firstarray to impart phase delays to the central portion of the beam. In thisway, the first biasing circuitry can control steering of a majority ofthe central portion of the beam within the target range of angles (orwithin a target volume). The second array can be arranged to surroundthe first array of pixels, and the second array can have a secondspatial frequency of N′, where N′>N. The second biasing circuitry canbias pixels of the second array to impart M different phase delays. Inthis way, the second biasing circuitry can control steering of amajority of the peripheral portion of the beam outside the target rangeof angles (or a target volume), where M is a number of different groupsof pixels in the second array.

Other embodiments of the disclosure may also be characterized as amethod of steering reflected light. The method can include arranging anSLM in a path of a coherent beam of light. The SLM can include asubstrate. The method may further include arranging a first array ofindividually-addressed reflective phase modulation pixels on thesubstrate having a first spatial frequency of N. The method may furtherinclude individually biasing pixels of the first array to impart aplurality of phase modulations to a central portion of the beam. Themethod may further include arranging a second array of border pixels onthe substrate surrounding the first array of pixels, the second array ofborder pixels having a second spatial frequency of N′, where N′>N. Themethod may yet further include biasing groups of pixels in the secondarray of border pixels to impart M phase modulations to a peripheralportion of the beam, where M is a number of different groups of pixelsin the second array of border pixels.

Other embodiments of the disclosure can be characterized as a spatiallight modulator including a first array of individually-addressedpixels, a second array of border pixels, and control circuitry. Thefirst array has a first spatial frequency and the second array has asecond spatial frequency, higher than the first. The border pixels canbe arranged around the first array. The control circuitry can be coupledto and biasing the first and second arrays to impart a plurality ofphase modulations to the individually-addressed pixels and to impart aplurality of phase modulations to the individually-addressed pixels andto impart an M number of phase modulations to the border pixels. M is anumber of electrically-connected groups of pixels in the second array. Adifferent phase modulation can be imparted to each of the groups.

BRIEF DESCRIPTION OF THE DRAWINGS

Various objects and advantages and a more complete understanding of thepresent disclosure are apparent and more readily appreciated byreferring to the following detailed description and to the appendedclaims when taken in conjunction with the accompanying drawings:

FIG. 1 illustrates a spatial light modulator system where light from asource is reflected off active pixels as well as a substrate of aspatial light modulator;

FIG. 2 illustrates a detailed view of the SLM of FIG. 1 showing thelight beam extending beyond an edge of the active array of pixels;

FIG. 3 illustrates a spatial light modulator system that isunder-filled;

FIG. 4 illustrates a detailed view of the SLM of FIG. 3 showing thelight beam under-filling the pixel array;

FIG. 5 illustrates a spatial light modulator with anindividually-addressed pixel array surrounded by a group-addressed pixelarray having a higher spatial frequency than the individually-addressedpixel array;

FIG. 6 illustrates a detailed view of one pattern for thegroup-addressed pixel array of FIG. 5;

FIG. 7 illustrates a detailed view of another pattern for thegroup-addressed pixel array of FIG. 5;

FIG. 8 illustrates a detailed view of yet another pattern for thegroup-addressed pixel array of FIG. 5;

FIG. 9 illustrates a detailed view of yet another pattern for thegroup-addressed pixel array of FIG. 5;

FIG. 10 illustrates a detailed view of biasing circuits for anembodiment of the individually-addressed and group-addressed pixelarrays for the SLM of FIG. 5;

FIG. 11 illustrates a detailed view of biasing circuits for anotherembodiment of the individually-addressed and group-addressed pixelarrays for the SLM of FIG. 5;

FIG. 12 illustrates two examples of a relation between pixel spatialfrequency and diffracted beam angles;

FIG. 13 illustrates an example of both pixel pitches describes in FIG.12 being used in combination;

FIG. 14 illustrates a method of steering reflected light according toone embodiment of this disclosure;

FIG. 15 illustrates a spatial light modulator with anindividually-addressed pixel array surrounded by a group-addressed pixelarray having a higher spatial frequency than the individually-addressedpixel array; and

FIG. 16 is a block diagram depicting physical components that may beutilized to realize the herein disclosed SLM's according to an exemplaryembodiment.

DETAILED DESCRIPTION

The present application relates to optical phase modulation. Morespecifically, but without limitation, the present disclosure relates toindividually-addressed reflective phase modulation pixels andgroup-addressed pixels of an SLM (or “border pixels”), where thegroup-addressed pixels have a higher spatial frequency than that of theindividually-address pixels.

The word “exemplary” is used herein to mean “serving as an example,instance, or illustration.” Any embodiment described herein as“exemplary” is not necessarily to be construed as preferred oradvantageous over other embodiments.

Preliminary note: The flowchart and block diagrams in the followingFigures illustrate the architecture, functionality, and operation ofpossible implementations of systems, methods and computer programproducts according to various embodiments of the present invention. Inthis regard, each block in the flowchart or block diagrams may representa module, segment, or portion of code, which comprises one or moreexecutable instructions for implementing the specified logicalfunction(s). It should also be noted that, in some alternativeimplementations, the functions noted in the block may occur out of theorder noted in the figures. For example, two blocks shown in successionmay, in fact, be executed substantially concurrently, or the blocks maysometimes be executed in the reverse order, depending upon thefunctionality involved. It will also be noted that each block of theblock diagrams and/or flowchart illustration, and combinations of blocksin the block diagrams and/or flowchart illustration, can be implementedby special purpose hardware-based systems that perform the specifiedfunctions or acts, or combinations of special purpose hardware andcomputer instructions.

The present invention is described more fully hereinafter with referenceto the accompanying drawings, in which embodiments of the invention areshown. This invention may, however, be embodied in many different formsand should not be construed as limited to the embodiments set forthherein. Rather, these embodiments are provided so that this disclosurewill be thorough and complete, and will fully convey the scope of theinvention to those skilled in the art. In the drawings, the size andrelative sizes of layers and regions may be exaggerated for clarity.Like numbers refer to like elements throughout.

It will be understood that, although the terms first, second, third etc.may be used herein to describe various elements, components, regions,layers and/or sections, these elements, components, regions, layersand/or sections should not be limited by these terms. These terms areonly used to distinguish one element, component, region, layer orsection from another region, layer or section. Thus, a first element,component, region, layer or section discussed below could be termed asecond element, component, region, layer or section without departingfrom the teachings of the present invention.

Spatially relative terms, such as “beneath,” “below,” “lower,” “under,”“above,” “upper,” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. It will beunderstood that the spatially relative terms are intended to encompassdifferent orientations of the device in use or operation in addition tothe orientation depicted in the figures. For example, if the device inthe figures is turned over, elements described as “below” or “beneath”or “under” other elements or features would then be oriented “above” theother elements or features. Thus, the exemplary terms “below” and“under” can encompass both an orientation of above and below. The devicemay be otherwise oriented (rotated 90 degrees or at other orientations)and the spatially relative descriptors used herein interpretedaccordingly. In addition, it will also be understood that when a layeris referred to as being “between” two layers, it can be the only layerbetween the two layers, or one or more intervening layers may also bepresent.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the invention. Asused herein, the singular forms “a,” “an,” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises”and/or “comprising,” when used in this specification, specify thepresence of stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of oneor more other features, integers, steps, operations, elements,components, and/or groups thereof. As used herein, the term “and/or”includes any and all combinations of one or more of the associatedlisted items, and may be abbreviated as “/”.

It will be understood that when an element or layer is referred to asbeing “on,” “connected to,” “coupled to,” or “adjacent to” anotherelement or layer, it can be directly on, connected, coupled, or adjacentto the other element or layer, or intervening elements or layers may bepresent. In contrast, when an element is referred to as being “directlyon,” “directly connected to,” “directly coupled to,” or “immediatelyadjacent to” another element or layer, there are no intervening elementsor layers present. Likewise, when light is received or provided “from”one element, it can be received or provided directly from that elementor from an intervening element. On the other hand, when light isreceived or provided “directly from” one element, there are nointervening elements present.

Embodiments of the invention are described herein with reference tocross-section illustrations that are schematic illustrations ofidealized embodiments (and intermediate structures) of the invention. Assuch, variations from the shapes of the illustrations as a result, forexample, of manufacturing techniques and/or tolerances, are to beexpected. Thus, embodiments of the invention should not be construed aslimited to the particular shapes of regions illustrated herein but areto include deviations in shapes that result, for example, frommanufacturing. Accordingly, the regions illustrated in the figures areschematic in nature and their shapes are not intended to illustrate theactual shape of a region of a device and are not intended to limit thescope of the invention.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this invention belongs. It will befurther understood that terms, such as those defined in commonly useddictionaries, should be interpreted as having a meaning that isconsistent with their meaning in the context of the relevant art and/orthe present specification and will not be interpreted in an idealized oroverly formal sense unless expressly so defined herein.

One type of spatial light modulator that can readily incorporate thisinvention is the Liquid Crystal On Silicon SLM. These devices typicallyuse the metallization layers deposited in an integrated circuitmanufacturing process for interconnect wiring within the device, andalso as a combined mirror/electrode layer that is used for reflectinglight and controlling a liquid crystal layer. Sometimes there arevariations, such as the incorporation of a dielectric reflector or theuse of non-standard processing for the mirror/electrode metal layer, butgenerally the array of pixels is defined by the patterning of that metallayer. The pixels are individually addressable, which is what gives themtheir utility in the optical system.

In one embodiment, this disclosure uses the same patterning techniquesthat are used to define the active pixels, but a mirror/electrodepattern of a higher spatial frequency than the active pixel array isdefined outside the active pixel array.

FIGS. 15 and 7 illustrates an SLM with an individually-addressed pixelarray surrounded by a group-addressed pixel array having a higherspatial frequency than the individually-addressed pixel array. Inparticular, SLM 1504 can include an individually-addressed pixel array1502 having a rectangular shape (although square, hexagonal, and othershaped arrays are also envisioned). Outside the individually-addressedpixel array 1502 can be a peripheral area comprising a group-addressedarray of pixels 1508 or electrodes. As shown, the group-addressed arrayof pixels 1508 extends to an edge of the SLM 1504, but this is notrequired. In some embodiments, the group-addressed array of pixels 1508or electrodes may extend to a border between the beam and the edges ofthe SLM 1504. In some cases, the beam may even spill over the edge ofthe group-addressed array of pixels 1508, depending on how the edge 1506of the beam is defined.

The group-addressed array of pixels 1508 can take a variety of formsincluding rows (e.g., FIG. 8), columns (e.g., FIG. 8), checkerboardpatterns (e.g., FIG. 6), etc. The group-addressed array of pixels 1508can be formed from mirrors and/or electrodes that can be controlled orbiased in a manner that causes a portion of the reflected light to besteered outside of a target range of angles (e.g., 0′ to the maximumtarget angle 1514). In other words, the individually-addressed pixelarray 1502 is biased or controlled to produce light that reflects at anangle that is less than or equal to a maximum target angle 1514. Thisrange of target angles or maximum target angle 1514 is referencedrelative to the SLM 1504 in FIG. 15. However, in embodiments, wherereflected light passes through a lens or lenses, the target range ofangles can refer to an output from the lens or lenses.

In order for the group-addressed array of pixels 1508 to redirect aportion of the beam outside of the target range of angels, thegroup-addressed array of pixels 1508 can have a spatial frequency, N′that is greater than the spatial frequency, N, of theindividually-addressed array of pixels 1502. In other words:

N′>N

Further, optical phase values of the mirrors/electrodes in thegroup-addressed array of pixels 1508 should alternate between valuesthat are approximately a half wave (7 t radians) apart. While aseparation of It radians is preferred, practically achieving such aprecise phase separation between mirrors/electrodes in thegroup-addressed array of pixels 1508 can be challenging. Thus, somevariance from this phase separation is allowable depending on thedemands of the application. In some embodiments, the mirrors/electrodesin the group-addressed array of pixels 1508 can have alternating phasevalues, such that adjacent mirrors/electrodes have phase levels thatdiffer by half a wave or a multiple thereof.

In some embodiments, the individually-addressed array of pixels can bebetween 256×256 and 1536×1536 pixels, and can include any square,rectangular, or other shape within these non-limiting bounds. In someembodiments, the pixels in the individually-addressed array of pixelscan be around 20 μm in width and/or length. In some embodiments, theindividually-addressed pixel array 1502 can have approximately a 300 Hzrefresh rate. In other embodiments, the individually-addressed pixelarray 1502 may be sized such that the pixels therein can achieve atleast a 25 Hz refresh rate, at least a 50 Hz refresh rate, 200 Hzrefresh rate, at least a 2 kHz refresh rate, or at least a 6 kHz refreshrate.

The maximum target angle 1514 can be defined as the angle of reflectedlight when the active pixels in the SLM 1504 are driven to a highestspatial frequency pattern. In one dimension, this pattern is analternating “high”, “low” phase pattern. The maximum diffractionefficiency into first-order spots may be achieved when the high and lowphase values differ by π. In this case, there is a theoretical maximumof approximately 40% of the light diffracted into each of the +/−firstorder beams, and the rest of the light is lost to higher orders.

It is generally considered that the useful range of angles is defined bythese beam directions, with the higher-order beams containing no usefulinformation representative of the pattern written to theindividually-addressed pixel array. For this reason, many opticalsystems will block the higher order light with an aperture, or otherwiseignore this wasted light. For the purposes of this disclosure, higherorder light is considered negligible and thus not discussed orconsidered.

Assuming illumination at normal incidence, the size of the maximumtarget angle, Omax (e.g., 1514 in FIG. 15) is given by

sin(θ_(max))=λ/2d

Where λ is the wavelength of the incident light, and d is the pixelpitch. This relationship is valid for both axes, and so an SLM withpixels disposed on a square array will be able to address a square inangle space.

If the border pixels are arranged to be addressable with a higherspatial frequency than the individually-addressed pixels, then, intheory, all the light that is incident on the border pixels may bediffracted “outside”, or to higher angle, than the target range ofangles. However, in practice, some light reflected from the borderpixels may leak into the target range of pixels (e.g., if there areimperfections in the border pixels, such as if the phase levelsimprinted on the light by the border pixels are not ideal, or if thereis inter-pixel leakage).

While FIG. 15 illustrates a generalized application where reflectionsfrom the individually-addressed array of pixels 1502 are directed into atarget range of angles, other embodiments may look to focus spots withina three-dimensional volume (e.g., Fourier holography). FIG. 5illustrates one example of a Fourier holography application. Here, theSLM 504 reflects a first portion of light from a source 510 toward oneor more lenses, such as lens 512, and the one or more lenses can focusthe light within a target volume. Group-addressed pixel array 508 canreflect a second portion of the beam through the one or more lenses, andpossibly partially outside the one or more lenses, to paths that areoutside the target volume. In particular, this second portion of lightmay be focused to one or more bright spots 520 that are exterior to thetarget volume. Thus, unlike prior art techniques that may form azero-order bright spot at a center of the target volume, the system 500of FIG. 5 directs the unwanted light to bright spots outside the targetvolume by using a group-addressed pixel array that has a higher spatialfrequency than the spatial frequency of the individually-addressed arrayof pixels 1502.

In other embodiments, the light may reflect off the SLM 504 multipletimes before reaching a target. For instance, a series of lenses andmirrors may be used in combination with the SLM 504.

FIGS. 6-8 illustrate embodiments of group-addressed pixel arrays havinga higher spatial frequency than the individually-addressed array ofpixels. For instance, the relationship of N′ over N for these examplesmay be around 2. However, N′ can be two or more times N. For instance,in FIG. 9 we see an example where N′/N is a little over 3.

Where the group-addressed array of pixels is formed from biasedelectrodes, biasing may be on device or off device. In other words, theSLM can include biasing devices on the SLM or contact pads that canprovide biasing currents and/or voltages from off-device power sources.

In some embodiments, all pixels in the group-addressed array of pixelscan be biased via the same polarity of AC signal, but the varyingoptical phases for each group of electrodes can be effected viadifferent AC amplitudes.

FIG. 10 illustrates an embodiment of an SLM where individually-addressedpixels are biased via individually-addressed pixel biasing device 1028and the group-addressed pixels are biased via group-addressed pixelbiasing devices 1024, 1026. The individually-addressed pixel biasingdevice 1028 can individually address each pixel within theindividually-addressed pixel array. The group-addressed pixel biasingdevices 1024, 1026 each are coupled to and bias some portion of theelectrodes in the group-addressed pixel array. In this example, each ofthe group-addressed pixel biasing devices 1024, 1026 bias alternatingvertical electrodes. The biasing of the group-addressed pixel biasingdevices 1024, 1026 is such that there are two groups of electrodes(e.g., alternating electrodes) that when biased, effect a phase delay toreflecting light that differs B*π (where B is any odd integer) betweenthe two groups. For instance, in the illustrated example, adjacentelectrodes produce a phase delay that differs from the two adjacentelectrodes by B*π.

FIG. 11 illustrates an example of a group-addressed array of pixelshaving three groups of electrodes (more than three are also possible).The individually-addressed array is again individually addressable andeach of the three groups of electrodes have a distinct bias provided byrespective group-addressed pixel biasing devices 1124, 1126, 1128. Thethree groups of electrodes could be driven to phase values separatedfrom adjacent neighboring electrodes by one third of a wave of phase.The group-addressed biasing can approximate a blazed grating, whichcould allow the energy incident on the group-addressed array of pixelsbe directed predominately in one direction (i.e., outside the targetrange of angles).

More generally, as long as a spatial frequency analysis of the patternfor the group-addressed pixel array does not show any components of alower spatial frequency than a highest spatial frequency that can berepresented by data written to the individually-addressed pixel array,any pattern and spacing can be used with the group-addressed pixelarray. The embodiment of N′>N and the phase difference between twogroups of electrodes/mirrors in the group-addressed pixel array, is justone practical way to achieve this more general rule.

These same descriptions would apply to design of group-addressed arraysof pixels formed from mirrors, except that the phase delays could be setduring mirror fabrication rather than via electrical biasing.

FIG. 12 illustrates two examples of a relation between pixel spatialfrequency and diffracted beam angles. The spatial frequency in the topfigure is lower than that in the bottom. In other words, the top figurecan represent a spatial frequency of individually-addressed pixels,while the bottom figure can represent a spatial frequency ofgroup-addressed pixels. In both figures there is a target window (e.g.,target range of angles). The top figure shows that the lower spatialfrequency results in a maximum diffracted beam that correspond to thetarget window (i.e., this pixel spacing enables individual biasing ofthe pixels to reflect light anywhere within the target window). Thebottom figure shows that the higher spatial frequency results in aminimum diffracted beam that corresponds to the target window (i.e.,this pixel spacing prevents reflected light from these pixels fromfalling within the target window). Said another way, by properlyselecting the spacing of pixels in the individually-addressed andgroup-addressed arrays, an SLM can be designed that causes lightincident outside the individually-addressed array of pixels to bereflected primarily (e.g., over 50% of this light) outside of the targetwindow.

FIG. 13 illustrates an example of both pixel pitches describes in FIG.12 being used in combination. The first array can beindividually-addressed, while the second array can be group biased.

FIG. 14 illustrates a method of steering reflected light usingindividually-addressed pixels and group-addressed pixels. The method caninclude arranging an SLM in a path of a coherent beam of light (Block1402). The SLM can include a substrate. The method may further includearranging a first array of individually-addressed reflective phasemodulation pixels on the substrate having a first spatial frequency of N(Block 1404). The method may further include individually biasing pixelsof the first array to impart a plurality of phase modulations to acentral portion of the beam (Block 1406). The method may further includearranging a second array of border pixels on the substrate surroundingthe first array of pixels, the second array of border pixels having asecond spatial frequency of N′, where N′>N (Block 1408). The method mayyet further include biasing groups of pixels in the second array ofborder pixels to impart M phase modulations to a peripheral portion ofthe beam, where M is a number of different groups of pixels in thesecond array of border pixels (Block 1410).

The foregoing is illustrative of the present disclosure and is not to beconstrued as limiting thereof. Although a few exemplary embodiments ofthis invention have been described, those skilled in the art willreadily appreciate that many modifications are possible in the exemplaryembodiments without materially departing from the novel teachings andadvantages of this disclosure. For example, the high spatial frequencyborder pixels need not be a simple multiple of theindividually-addressed array's spatial frequency, and the edges of someof the peripheral pixels need not be aligned with theindividually-addressed pixels. In another example, the pattern of theperipheral pixels could be stripes that are angled with respect to anedge of the individually-addressed array, or the pattern of peripheralpixels could contain components of high spatial frequencies in more thanone direction such as a fine checker-board, or a hexagon pattern. Notealso that the disclosure can be implemented in either transmissive orreflective SLMs. While it may be easier to block peripheral illuminationin a transmissive device, it may not be desirable to do so in the caseof high-power systems. For these systems, it may be preferable todiffract the “overfill” light to a safe beam dump somewhere else in thesystem rather than have the energy blocked by the SLM itself. Theindividually-addressed pixels can also take a square, hexagonal, orother shape as compared to the rectangular individually-addressed arraysdiscussed above. Another example is an SLM in which the peripheral areais broken up into several “zones”. Due to normal constructionvariations, these zones may demand somewhat different driving signals toproduce the desired modulation. This may be accomplished by wiring themto more input connectors. Note also that the signals for driving theperipheral electrodes may be generated on the device itself usingstandard electronic techniques.

Accordingly, many different embodiments stem from the above descriptionand the drawings. It will be understood that it would be undulyrepetitious and obfuscating to literally describe and illustrate everycombination and sub-combination of these embodiments. As such, thepresent specification, including the drawings, shall be construed toconstitute a complete written description of all combinations andsub-combinations of the embodiments described herein, and of the mannerand process of making and using them, and shall support claims to anysuch combination or sub-combination.

In the specification, there have been disclosed embodiments of theinvention and, although specific terms are employed, they are used in ageneric and descriptive sense only and not for purposes of limitation.Although a few exemplary embodiments of this invention have beendescribed, those skilled in the art will readily appreciate that manymodifications are possible in the exemplary embodiments withoutmaterially departing from the novel teachings and advantages of thisinvention. Accordingly, all such modifications are intended to beincluded within the scope of this invention as defined in the claims.Therefore, it is to be understood that the foregoing is illustrative ofthe present invention and is not to be construed as limited to thespecific embodiments disclosed, and that modifications to the disclosedembodiments, as well as other embodiments, are intended to be includedwithin the scope of the appended claims. The invention is defined by thefollowing claims, with equivalents of the claims to be included therein.

The methods described in connection with the embodiments disclosedherein may be embodied directly in hardware, in processor-executablecode encoded in a non-transitory tangible processor readable storagemedium, or in a combination of the two. Referring to FIG. 16 forexample, shown is a block diagram depicting physical components that maybe utilized to realize the SLM (and the control circuitry for biasingthe pixels) according to an exemplary embodiment. As shown, in thisembodiment a display portion 1612 and nonvolatile memory 1620 arecoupled to a bus 1622 that is also coupled to random access memory(“RAM”) 1624, a processing portion (which includes N processingcomponents) 1626, an optional field programmable gate array (FPGA) 1627,and a transceiver component 1628 that includes N transceivers. Althoughthe components depicted in FIG. 16 represent physical components, FIG.16 is not intended to be a detailed hardware diagram; thus many of thecomponents depicted in FIG. 16 may be realized by common constructs ordistributed among additional physical components. Moreover, it iscontemplated that other existing and yet-to-be developed physicalcomponents and architectures may be utilized to implement the functionalcomponents described with reference to FIG. 16.

This display portion 1612 generally operates to provide a user interfacefor a user, and in several implementations, the display is realized by atouchscreen display. In general, the nonvolatile memory 1620 isnon-transitory memory that functions to store (e.g., persistently store)data and processor-executable code (including executable code that isassociated with effectuating the methods described herein). In someembodiments for example, the nonvolatile memory 1620 includes bootloadercode, operating system code, file system code, and non-transitoryprocessor-executable code to facilitate the execution of a methoddescribed with reference to FIG. 14 described further herein.

In many implementations, the nonvolatile memory 1620 is realized byflash memory (e.g., NAND or ONENAND memory), but it is contemplated thatother memory types may be utilized as well. Although it may be possibleto execute the code from the nonvolatile memory 1620, the executablecode in the nonvolatile memory is typically loaded into RAM 1624 andexecuted by one or more of the N processing components in the processingportion 1626.

The N processing components in connection with RAM 1624 generallyoperate to execute the instructions stored in nonvolatile memory 1620 toenable control of the individually-addressed pixels of the SLM. Forexample, non-transitory, processor-executable code to effectuate themethods described with reference to FIG. 14 may be persistently storedin nonvolatile memory 1620 and executed by the N processing componentsin connection with RAM 1624. As one of ordinarily skill in the art willappreciate, the processing portion 1626 may include a video processor,digital signal processor (DSP), micro-controller, graphics processingunit (GPU), or other hardware processing components or combinations ofhardware and software processing components (e.g., an FPGA or an FPGAincluding digital logic processing portions).

In addition, or in the alternative, the processing portion 1626 may beconfigured to effectuate one or more aspects of the methodologiesdescribed herein (e.g., the method described with reference to FIG. 14).For example, non-transitory processor-readable instructions may bestored in the nonvolatile memory 1620 or in RAM 1624 and when executedon the processing portion 1626, cause the processing portion 1626 toperform individual addressing of the active pixels. Alternatively,non-transitory FPGA-configuration-instructions may be persistentlystored in nonvolatile memory 1620 and accessed by the processing portion1626 (e.g., during boot up) to configure the hardware-configurableportions of the processing portion 1626 to effectuate the functions ofthe individually-addressed pixel biasing device 1028.

The input component 1630 operates to receive signals that are indicativeof one or more aspects of control of the active pixels. The outputcomponent generally operates to provide one or more analog or digitalsignals to effectuate an operational aspect of theindividually-addressed pixel biasing device 1028. For example, theoutput portion 1632 may provide control signals for individuallyaddressing the active pixels.

The depicted transceiver component 1628 includes N transceiver chains,which may be used for communicating with external devices via wirelessor wireline networks. Each of the N transceiver chains may represent atransceiver associated with a particular communication scheme (e.g.,WiFi, Ethernet, Profibus, etc.).

As will be appreciated by one skilled in the art, aspects of the presentinvention may be embodied as a system, method or computer programproduct. Accordingly, aspects of the present invention may take the formof an entirely hardware embodiment, an entirely software embodiment(including firmware, resident software, micro-code, etc.) or anembodiment combining software and hardware aspects that may allgenerally be referred to herein as a “circuit,” “module” or “system.”Furthermore, aspects of the present invention may take the form of acomputer program product embodied in one or more computer readablemedium(s) having computer readable program code embodied thereon.

As used herein, the recitation of “at least one of A, B and C” isintended to mean “either A, B, C or any combination of A, B and C.” Theprevious description of the disclosed embodiments is provided to enableany person skilled in the art to make or use the present disclosure.Various modifications to these embodiments will be readily apparent tothose skilled in the art, and the generic principles defined herein maybe applied to other embodiments without departing from the spirit orscope of the disclosure. Thus, the present disclosure is not intended tobe limited to the embodiments shown herein but is to be accorded thewidest scope consistent with the principles and novel features disclosedherein.

1. A spatial light modulator having a plurality of reflective phasemodulation pixels, the spatial light modulator comprising: a first arrayof reflective phase modulation pixels having a first spatial frequencyof N, and configured to apply a plurality of phase modulations to acentral portion of a beam reflecting off the first array of pixels; afirst biasing circuitry coupled to the first array of pixels that biasesthe first array of pixels to impart phase delays to the central portionof the beam, thereby steering a majority of the central portion of thebeam within a target range of angles; a second array of border pixelsarranged to surround the first array of pixels, the second array ofpixels having a second spatial frequency of N′, where N′>N, andconfigured to apply M different phase modulations to a peripheralportion of the beam; and a second biasing circuitry coupled to thesecond array of pixels that biases the second array of pixels to impartthe M different phase delays to a majority of the peripheral portion ofthe beam, thereby steering a majority of the peripheral portion of thebeam outside the target range of angles, where M is a number ofdifferent groups of pixels in the second array.
 2. The spatial lightmodulator of claim 1, wherein M=1 or
 2. 3. The spatial light modulatorof claim 2, wherein each of the two-phase delays differs from the otherby B*π, where B is an odd integer.
 4. The spatial light modulator ofclaim 1, wherein the first biasing circuitry individually addressespixels in the first array, and the second biasing circuitry addressesgroups of electrodes in the second array.
 5. The spatial light modulatorof claim 1, wherein the border pixels are arranged in rows, columns, ora checkerboard.
 6. The spatial light modulator of claim 1, the firstarray of pixels has two or more spatial frequencies, and wherein N is ahighest spatial frequency thereof, and wherein the second array ofpixels has two or more spatial frequencies, and wherein N′ is a lowestspatial frequency thereof.
 7. The spatial light modulator of claim 1,wherein the second array of pixels comprises mirrors.
 8. A method ofsteering reflected light, the method comprising: arranging an SLM in apath of a coherent beam of light; arranging a first array ofindividually-addressed reflective phase modulation pixels to have afirst spatial frequency of N; individually biasing pixels of the firstarray to impart a plurality of phase modulations to a central portion ofthe beam; arranging a second array of border pixels surrounding thefirst array of pixels, the second array of border pixels having a secondspatial frequency of N′, where N′>N; biasing groups of pixels in thesecond array of border pixels to impart M phase modulations to aperipheral portion of the beam, where M is a number of different groupsof pixels in the second array of border pixels.
 9. A spatial lightmodulator comprising: a first array of individually-addressed pixelshaving a first spatial frequency; a second array of border pixelsarranged around the first array, and having a second spatial frequencyhigher than the first spatial frequency; control circuitry coupled toand biasing the first and second arrays to impart a plurality of phasemodulations to the individually-addressed pixels and to impart an Mnumber of phase modulations to the border pixels, where M is a number ofelectrically-connected groups of pixels in the second array, and adifferent phase modulation is imparted to each of the groups.